The present invention relates to a high voltage circuit breaker having a contact system, a contact driven by a switch mechanism, and a counter-contact opposite the contact and driven by a transmission element. An auxiliary gear is formed by a multiple transmission elements. The contact is electrically connected to a first electric terminal of the high voltage circuit breaker. The counter-contact is electrically connected to a second electric terminal of the high voltage circuit breaker via a current path.
Such a high voltage circuit breaker is described in, for example, European Patent No. 0 313 813. This patent describes a contact driven by a switch mechanism, where a stud-shaped counter-contact can also be driven to increase the contact separation rate in a shutdown operation in particular. The motion of the driven contact is transmitted to the counter-contact by motion transmission elements or an auxiliary gear, driving the counter-contact in the direction of motion opposite that of the contact.
French Patent 2 491 675 also describes a high voltage circuit breaker where a driven contact and a counter-contact driven in the opposite direction by an auxiliary gear and by motion transmission elements are provided.
European Patent Application 0 25 833 A1 also describes a high voltage circuit breaker where a contact and a counter-contact are linked by a gear and can be driven in opposite directions in the event of shutdown.
An object of the present invention is to provide a high voltage circuit breaker of the type defined in the preamble such that its lifetime is lengthened in comparison with that of conventional switches.
This object is achieved according to the present invention by the fact that a parallel current path which is electrically parallel to the current path and leads from the counter-contact to the second terminal of the high voltage circuit breaker by way of the transmission elements is interrupted by an insulation area. At least one of the transmission elements may be designed so that it is electrically insulating in order to interrupt a parallel current path formed in parallel to the main current path between the counter-contact and the second terminal of the high voltage circuit breaker.
Conventional high voltage circuit breakers have in common the fact that the counter-contact is driven by an auxiliary gear and transmission elements which are connected at least in part to stationary parts of the switch, e.g., for bearing purposes. For example, gearwheels or levers must be pivotingly mounted at a fixed point.
This fails to take into account the problem that a parallel current path is thus created from the counter-contact to the second terminal of the circuit breaker by way of the auxiliary gear or the motion transmission elements; this current path is parallel to the main current path leading from the counter-contact to the second terminal usually by way of slide contacts.
The drive mechanism for the counter-contact is destroyed or at least damaged after a few switching cycles due to the electric load, because motion transmission elements and auxiliary gear are not normally designed to carry high currents such as those occurring in the event of a short circuit, for example.
Due to the method of achieving the object of the present invention, current flow outside the main current path is completely prevented, so that mechanical parts cannot be damaged due to such a current flow.
Furthermore, this also prevents the effects of magnetic forces occurring due to parallel current-carrying current paths which can have a negative effect on the contact pressure in the case of slide contacts, for example, due to lifting of the contact fingers.
An advantageous embodiment of the present invention provides for the end of the counter-contact facing away from the contact to be made of insulating material in the area of the point of action of the transmission elements.
Thus, the auxiliary current path from the counter-contact over the auxiliary gear to the second terminal of the circuit breaker is interrupted at the point of action of the transmission elements on the counter-contact.
Another advantageous embodiment of the present invention provides for at least one bearing or one shaft of the auxiliary gear to be made at least partially of an insulating material.
Additional advantageous embodiments of the present invention provide for a stud of the auxiliary gear sliding in a sliding guide to be made at least in part of insulating material or a sliding guide of the auxiliary gear to be made of an insulating material.